Conventional lubricating devices, such as grease guns, do not provide a precisely measured volume of lubricant. It is merely possible to develop by experience a knowledge of how much lubricant is discharged with each pull of the trigger. However, it is important that precisely measured quantities of lubricant are supplied to certain equipment such as the drives for the control surfaces and flaps in the wing and tail section of an aircraft. A precisely dosed discharge of lubricant is especially important in those instances where the conventional spindle drives have been replaced by so-called rotary gear drives. Such rotary gear drives are enclosed in a housing, but due to their required construction lubricant is discharged outwardly and moisture and contaminations can enter into the housing of the rotary gear. Further, such rotary gear drives are constructed to have a working life typically within the range of ten to twenty years without the need for a complete overhaul. In order to ensure such a life span while avoiding a complete overhaul, it is important that a precise quantity of lubricant is periodically replaced. The precise dosing is necessary, especially with regard to changes in the viscosity of the lubricant in response to temperatures. In other words, over-filling of the gear boxes of such rotary gear drives must be avoided.
The foregoing precise supply of a lubricant quantity or rather volume has not been satisfactorily solved heretofore. Such devices must provide not only an exact dosing, but must also be highly efficient in their use so that a multitude of sequential lubricating operations can be efficiently performed.